Antibodies directed toward morphine, lysergamide, cannabis, normetanephrine, beta-3,4-dimethoxyphenethylamine 2,5-dimethoxy-4-methylphenylisopropylamine, mescaline, meperidine and related congenera as well as nicotine and its metabolites have been produced in experimental animals, and efforts are being continued to extend this list to other pharmacologically active substances of neurochemical interest. These antibodies will be characterized and radioimmunoassays developed to detect these compounds in picogram quantities in biological fluids and tissues. These antibodies will also be used to locate these compounds in the target cell. The ability of the antibodies to combine with and neutralize the effects of pharmacologically active substances may permit the neurochemist to use them as specific inhibitors in in vitro and in vivo experiments. A radioimmunoassay for N,N-dimethylindoleamines will be used to estimate this family of pharmacologically active compounds and potential endogenous psychotogens in physiological fluids and tissue and to determine indole(ethyl)amine-N-methyltransferase activity. With the availability of a radioimmunoassay for nicotine and its metabolites it is now possible to determine if a relationship exists between blood levels of nicotine metabolites and smoking behavior.